There is a continuing progress of technology of the packet radio communication. The packet radio communication has many advantages over other communication system. On the other hand, there are some problems that are attributed to the characteristic of a radio communication. One of the problems is fading.
Fading is the phenomenon of a fluctuation in intensity of received radio waves while the adjustments of sending and receiving apparatus remain unchanged. In the presence of fading, packet error easily arises during packet radio communicating. It is well known that there is relationship between the ratio of packet length to period of fluctuation of fading and a packet error rate. In particular, packet error easily arises, as the packet length is longer to the period of the fluctuation.
Therefore, it is important to investigate the relationship between the ratio of packet length to the period of fluctuation of fading and an error occurrence state of packet. It is possible to investigate the state of fading period, for example, by using electric field intensity measuring set. It is also possible to investigate error status of packet, for example, by using line monitor. However, there is not the method, which is capable of graphically and simultaneously indicating the fading period and an error occurrence state of packet.